1. Inconsistent hue and brightness of Bai Keding
Most products in tinplate printing require the application of white Ding Can white, which actually simulates the effect of paper white. As for the currently used white cauldrons, there are basically no colors that can be slightly biased towards pure white, such as yellow cauldrons, red cauldrons, blue cauldrons, red and blue cauldrons (purple cauldrons), and each type of white cauldron has a different degree of whiteness. These elements determine different hues, and the whiteness of white can have different effects on the hue of ink. For example, in the blue or blue red stage of T-block printing, the color of a certain warm color printing will be darker than the ink itself; On the contrary, in the yellow stage of thong printing, the printing color will be slightly more yellow than the ink itself, resulting in a yellow green color.
In short, ink with a specific red color can be used as a complementary color for printing, while blue red color (purple color) can be used as a complementary color for printing, resulting in darker printing colors than the ink itself; The green phase specific ink can be printed in its complementary colors, such as the red phase and the blue red phase (purple phase), but the printing color will be darker than the ink itself; The specific ink with blue phase can be either yellow or yellow phase in its complementary color, and the printed color will be darker than the ink itself.
2. Ink discoloration after high-temperature baking
Iron ink is an important technical indicator of thermosetting ink, and its color remains unchanged after high-temperature baking. However, some hues of ink in actual production may change color to some extent after high-temperature baking, such as white ink, diluted ink, and ink distributed with a large amount of white ink or diluted ink. After repeated baking, yellowing may occur, especially when a large amount of diluent is used to modulate colors, which can cause significant color changes after baking. For example, after adding a large amount of diluent to blue ink, it is formulated into light blue ink, which may turn into deep blue after repeated baking. Process designers should fully consider this when developing printing processes. After repeated baking, the ink will simply change color during the final printing.
3. Color changes before and after polishing
The final process of printing is polishing, which aims to maintain the image and prevent damage, as well as improve gloss and add appearance. Generally speaking, after high temperature, the printed iron varnish will turn yellow, and the gloss layer has a higher reflectivity to light, so the color of the ink will generally be brighter than before light. But some light oils contain whitening agents, so under blue light irradiation, the gloss color of the ink will be more than the original blue overall color after using this light oil product, which is the combination of ink color and light oil blue.
4. Gold and silver ink, or metallic ink made by dividing gold and silver ink, may undergo color changes after oxidation
Imprinted gold and silver ink are colored from metal powders such as copper and aluminum, while embossed gold ink is processed by grinding copper powder; Ink is a printing ink made from ground aluminum powder.
The chemical properties of gold and silver ink in copper powder and aluminum powder are generally unstable. When encountering acid, alkali, water vapor, sulfide gas or carbonate gas, chemical reactions will occur, causing the ink color to lack metallic color. The color change of gold ink is from gold to brownish red, and then to partial black. Due to the initial oxidation of copper, red cuprous oxide is generated, which further oxidizes to produce black cuprous oxide. Tonight, copper powder in the presence of thick carbon dioxide gas and high moisture simply turns into alkaline copper carbonate, and the printing quality of gold ink gradually fades. The color after silver ink is gray, lacking the metallic texture of silver. In the actual operation of gold and silver ink, try to open the can and print it out as much as possible. The production of the remaining ink should pay special attention to its future use, and can only be used after the color has not been changed.
5. Printing ink layer thickness varies
If the printing thickness of the same ink is different, its color will also be different. In actual printing, the thickness of the ink layer is controlled by printing pressure and ink volume. Generally speaking, the printing pressure will not change after reasonable adjustment. Therefore, the thickness and uniformity of the ink layer in printing are achieved by manipulating the ink volume. Most printing machines in China still manually adjust the ink volume to control the ink volume. Due to the influence of many factors on manual adjustment, the thickness of the ink layer may be uneven, resulting in different shades, colors, and standard colors of the ink.
6. Unclean cleaning of ink rollers in printing machines
Cleaning the ink roller is the most basic requirement for printing. Nowadays, tinplate printing generally uses two-color printing machines, which can print two colors at a time. However, most iron printing products require printing four or more colors and need to be printed twice or more to complete. So after printing the first two colors of ink, it is necessary to clean the drum and then ｒｅｐｌａｃｅ the other two colors of ink. If the ink roller is not cleaned thoroughly and remains on the ink of the previous color, the color will change after printing, such as red when printing with the previous color, and green will darken when printing with green.
